[barryhunter]

tinyurl and other shorteners generally use a 301 redirect, which often does pass 'link juice'.

nofollow is usually under the control of the webmaster. Which may or may not be the same as the content creator.

Think forums and blog comments, as poster you generally have no control if nofollow is added to links. Usually it should be, but no garentee.

Also think of sites like twitter, facebook and g+, again you can't ensure that nofollow is added. Similally when that content is then copied or syndicated. You can usually hope that the copier will perserve the link itself, but they may or may not choose to 'nofollow' the copied link.

And lastly, 'bad' bots, may well ignore the nofollow anyway. It would have to be broken/clever bot to get the destiniation from donotlink